Japanese Patent Publication Open to Public Inspection--hereinafter referred to as `JP OPI Publication- No. 61-149272/1986`, for example, has so far proposed a technique relating to the preparation of an electrophotographic photoreceptor, in which a coating solution containing a photoconductive composite is coated on a cylindrical substratum in a dip-coating method.
In the above patent publication, a substratum having one end closed and the other end opened has been used as a cylindrical substratum. When the substratum is coated by dipping it in a coating solution from its open end, the patent publication describes that it would be preferred to keep a coating room temperature T.sub.A (or the air temperature of the substratum) equivalent to or relatively little higher than a coating solution temperature T.sub.L. For example, it describes that, if a substratum thickness is not thinner than 1 mm, the relation between the two temperatures is preferably -2.degree. C..ltoreq.T.sub.A -T.sub.L .ltoreq.10.degree. C. and, if a substratum thickness is not thicker than 1 mm, the relation therebetween is preferably -1.degree. C..ltoreq.T.sub.A -T.sub.L .ltoreq.3.degree. C. The proposal of the above patent publication paid attention to the temperature characteristics when a substratum is coated. However, post-process treatments to be made after completing a coating process are also very important from the viewpoint of preparing an electrophotographic photoreceptor.
Therefore, JP OPI Publication No. 58-207050/1983 discloses a technique for forming a photoreceptor, in which, after completing a coating process in a coating method such as a dip-coating, a spray-coating, a spin-coating, a spinner-coating or a blade-coating method by making use of an apparatus such as shown in FIG. 3, the coated substratum is then dried with hot air, so that a photoreceptor can be formed. The specification of this patent publication gives the examples of photoreceptors each comprising a photoreceptive layer having a layer structure multilayered with a carrier generation layer and a carrier transport layer. In the examples, each of the layers are dried up with hot air at a temperature of 130.degree. C.
However, in the above-mentioned preparation processes carried out with such a hot air-drying treatment as described above, the electrophotographic characteristics are deteriorated, because a thin-coated layer such as an under layer or a carrier generation layer is so fatigued as to be deteriorated by an excess drying treatment and a heat treatment. In the case of a carrier generation layer, a coating unevenness produced in a coating process and dispersed-grain flocculates are rapidly dried-and-fixed without any spare time to deflocculate them, so that there raise the problems that any uniform image cannot be produced because of a charging unevenness and photosensitivity unevenness produced in forming an image.